The present invention relates to furniture, and in particular to a height adjustor device therefor.
Height adjustors are typically used in conjunction with various types of furniture, such as tables, chairs, and the like, to vary the height of the supporting surface of the furniture above the ground. Dental chairs, drafting stools, operating chairs, and the like are examples of that type of furniture in which height adjustors are used.
Pneumatic and hydraulic cylinders are generally used in adjustable chairs to raise and lower the seat. Pneumatic cylinders not only provide means for adjusting the seat height, but also form a resilient column or shock absorber to improve comfort. Although this combination of features is quite desirable, the seals on such pneumatic cylinders tend to wear quickly during most types of use, thereby effectively ruining the integrity of the cylinder. A major cause of such seal damage is the application of lateral of off-centered forces to one end of the cylinder, while holding the other end of the cylinder in a static or fixed position. These lateral forces are particularly destructive when the chair is in the fully extended position, wherein the forces are effectively applied at a relatively long lever arm.